DHCP Advantages

If you have a local network, commonly called a Local Area Network, or LAN, you know that administering it can be a chore. If you ever change IP address ranges, or the gateway to the Internet, then changing all of the computers can take some time.

By using Dynamic Host Configuration Protocol, or DHCP for short, these changes can be administered in one place. The changes are then picked up by the other computers on the network.

To do this, there needs to be a machine that acts as a DHCP server. This is a computer with a Windows server operating system or Linux operating system in our customer base. Most Internet routers have the capability of running as a DHCP server as well.

The DHCP works by supplying an IP information set on a lease to the requesting LAN node. Leases can have a short life by default, so if you need to use the same IP over a long period of time, perhaps as part of registering software, be sure you understand how to configure lease assignment on your DHCP server.

When a computer boots up, instead of having the IP information set, it is told to get the information from a DHCP server. It does this by sending a request out on the network, and listening for a reply. The request is a broadcast type, so the location of the DHCP server does not need to be known. It just needs to be on the same network.

When the DHCP server detects a request, it responds to the machine sending the request. The request is answered by sending IP information to the requesting machine. This would include an IP address, and subnet mask, as the minimum. Normally, it also includes the address of the Internet gateway, and DNS servers. With that information, the requesting machine has what is needed to get on the local network, and route requests to the Internet.

Let’s say that the Internet gateway changes. Using DHCP, the DHCP server you update the new gateway address. When the machines on the network update their IP information, which is done automatically on a periodic basis, they get the new gateway address.

At our offices, we have two possible Internet gateways. If the one that is currently being used needs to be taken down for maintenance, for example; the DHCP servers are changed to use the other Internet gateway. Within a relatively short period of time, all of the computers on our local network get updated, and use the other gateway. Once they are all using the other gateway, then the first one can be taken down for maintenance, and the users do not see anything different.

Using DHCP is another way that you can centralize your system administration, and avoid having to go from computer to computer when something changes.